The cost is only for distribution. By default it's whom distributes the spot that the charges will go to.
The cost for distributing a spot is 35€ x group of channels. For example:
1 spot for 2 channels = 1 spot x 2 channels x 35€ = 70€. Another example: 2 spots for 1 channel each = 2 spots x 1 channel x 35€ = 70€.
The bill is sent via e-mail in the beggining of the month following the consumption.